Eleven people accidentally inhaled a significant amount of a gaseous mixture of hydrogen chloride, phosphorus oxychloride, phosphorus pentachloride, oxalyl chloride, and oxalic acid. Clinical observations and laboratory tests were recorded from the time of admission throughout hospitalization. The main abnormalities were found in the respiratory tract and consisted of clinical and physiologic evidence of obstruction of the airways, mild interstitial and alveolar edema, a defect in diffusion, and inequalities of ventilation and perfusion that produced hypoxemia. All of these cleared within a short time.